Traditionally, a spring core for a mattress has comprised a plurality of aligned coil springs, each coil spring having an upper end turn and a lower end turn interconnected by one or more turns or revolutions of the spring. All of the coil springs are of approximately identical height so that all of the upper end turns lie in a common top plane and, similarly, all of the lower end turns lie in a common bottom plane. The spring core typically has a longitudinal dimension and a transverse dimension, the longitudinal dimension being greater than the transverse dimension. The coil springs are aligned in longitudinally extending columns and transversely extending rows. The coils springs are typically joined by helical lacing wires located in the top and bottom planes of the spring core, each helical lacing wire encircling the end turns of adjacent rows or columns of coil springs. Thus, the helical lacing wires may extend either transversely connecting adjacent rows of coil springs or longitudinally connecting adjacent columns of coil springs. Often, a rectangular border wire is located in the top and bottom planes of the spring core and the outermost coil springs clipped or otherwise secured to the border wires.
Alternatively, a mattress spring core may be formed with bands of springs rather than individual coil springs. Each of these bands of springs is formed of a single piece or length of wire formed into a plurality of connected coil springs, each coil spring having an upper end turn and a lower end turn. Adjacent bands of coil springs are again joined by helical lacing wires. Most often these continuous bands of springs extend longitudinally and the helical lacing wires extend transversely of the bands and embrace portions of the bands. Several different kinds of bands of springs have been proposed for incorporation into spring interiors of bedding mattresses. One kind of band which is the subject of British Patent No. 2,143,731 will hereinafter be referred to as a band of interlocked or interlaced springs. In addition, U.S. Patent Nos. 4,053,956 and 4,112,726 disclose bands of springs made of a single length of wire without the convolutions of the coil springs being interlocked or interlaced. In either case, such a band comprises a single length of wire configured to form a plurality of individual coil springs arranged in a row, one end turn of each coil spring lying adjacent to a top face of the band and the other end turn of the coil spring lying adjacent to a bottom face of the band, each coil spring being of a rotational hand either opposite to or of the same rotational hand of the adjacent coils immediately before it in the row and being joined to the adjacent coil springs by a plurality of interconnecting segments of wire integral with the coil springs. One of the pair of interconnecting segments is located in the bottom face of the band and the other of the pair of interconnecting segments is located in the top face of the band.
Regardless of whether a mattress spring core is made of a plurality of aligned individual coil springs or a plurality of interconnected bands of coil springs, the end turns of the coil springs must be connected together in order to maintain the alignment of the coil springs in the spring core. Helical lacing wires, clips, or hog rings are the most common forms of connectors used to connect adjacent end turns of adjacent rows or columns of coil springs. If helical lacing wires are used, a machine is required to apply the helical lacing wires, increasing the cost of the final product.
One well known type of spring interior of a mattress or cushion which does not require helical lacing wires or their equivalent to connect adjacent rows or columns of coil springs is a so called pocketed spring assembly. One type of pocketed spring assembly comprises a plurality of fabric pockets joined together, each pocket containing an individual coil spring. The row of pocketed coil springs may be individual coil springs joined to each other as in U.S. Pat. No. 4,234,983 or a band of springs formed from a single continuous wire as in U.S. Pat. No. 5,127,635. The individual pockets are then joined together as by sewing, welding or adhering to form a pocketed spring assembly.
U.S. Pat. No. 5,669,093 issued to the assignee of the present invention and herein incorporated by reference discloses a plurality of integrally connected fabric tubular blocks, each tubular block containing a band of coil springs. The tubular blocks are connected to each other accordion style by lines of attachment between the individual blocks with successive lines of attachment being located alternately in the upper and lower planar surfaces of the assembly. The method of assembly of such a pocketed product is disclosed in U.S. Pat. No. 5,761,784 which is also incorporated by reference herein.
Another patent which discloses a pocketed spring assembly is U.S. Pat. No. 5,127,635 also issued to the assignee of the present invention. This patent discloses a pocketed coil spring assembly in which longitudinally extending bands of coil springs made of one continuous length of wire are enclosed in fabric covers to form longitudinally extending strips. Within each strip, individual pockets encasing one or more coil springs of a band are formed by connecting opposite sides of the fabric together between the individual coil springs. The fabric pockets are adhesively secured together by conventional adhesive with or without foam pieces inserted between the longitudinally extending strips.
Another known type of spring assembly comprises a plurality of three-sided spring containing strips joined together in order to make a spring assembly. Each strip contains a plurality of individual coil springs placed within a three-sided strip or pocket of fabric, one side of the strip being open. The individual coil springs within the strip are separated from each other by individual fabric partition members which are sewn or otherwise secured to the top and bottom of the three-sided fabric strip. A plurality of strips are aligned and sewn together in order to make the desired size of spring assembly. U.S. Pat. Nos. 1,663,272 and 1,724,948 disclose such spring containing strips and spring assemblies. One disadvantage to this type of spring assembly is that a separate piece of fabric (partition member) must be sewn between each individual coil spring thus increasing the time and labor costs required to make a strip and an assembly of strips.
British Patent No. 379,029 likewise discloses a plurality of spring containing members joined together in order to make a spring assembly. However, each of these members comprises a pair of fabric strips. One of the strips surrounds the upper end turns of each coil spring of the member and, the other fabric strip encompasses the lower end turns of each coil spring within the member. However, each strip requires a great deal of stitching in both the longitudinal and transverse directions in order to secure the end turns of the coil springs in place.
It has been one objective of the present invention to create a string or row of springs joined together more economically than has heretofore been possible.
It has been another objective of the invention to economically join together a plurality of strings of springs into a spring assembly by securing adjacent fabric retainers to each other.
It has been another objective of the present invention to economically create a string or row of springs by securing a continuous band of coil springs within the string by means of a pair of retainers of fabric material.
It has further been an objective of the present invention to provide a spring assembly in which strings of springs are encased within tubular fabric blocks and multiple blocks joined together to make a spring assembly.